Please note, this diopter correction lens will not fit the M10, M10-P, M10-D, M10-R or M10 Monochrom. The correct diopter can be found here: Leica M10 Correction lens II, +1.5 diopter

Leica Diopter Correction Lenses provide near or far-sighted users a clear viewfinder image without the use of eyeglasses. Ten Diopter Correction Lenses are available, from -3 to +3.

For the M series. Screws onto viewfinder eyepiece.